SPLIT THE BABY, DRINK THE POISON, CARRY THE HOT IRON, SWEHR ON THE BIBLE. HOW COURTS EXPLOIT SUPERSTITION TO UNCOVER HIDDEN TRUTHS.

YOU PROBABLY REMEMBER thestory of King Solomon and the baby. Two women come before the monarch claiming to be a child's mother. Neither has evidence to show. So Solomon proposes the following: He'll cut the baby in half. Each woman will receive an equal share. This will be equitable, if a bit messy.

On the face of it, the king was either a baby-hating madman or an idiot. Killing an infant and divvying up its corpse hardly seems like a reasonable response to a maternity dispute. But if you know the story, you know what Solomon had in mind: The baby's true mother would rather sacrifice her child's custody than her child's life. She would turn down the king's proposal, and then he would award the baby, in its entirety, to her.

We can learn a couple of things from Solomon. First, judicial procedures that seem downright stupid may in fact be very wise. Second, when "ordinary" evidence is lacking, judicial officials may still be able to get to the bottom of things by creating clever rules--even ones that are based on a lie ("when maternity is in doubt, cut the child in half "). Such clever rules can manipulate people's incentives, leading them to reveal information only they have access to through the choices they make.

BURN, BABY, BURN

"ORDEALS" WERE MEDIEVAL European judicial officials' version of splitting the baby. From the ninth through the 13th centuries, two types flourished: hot and cold.

In a hot water ordeal, a priest boiled a cauldron of water into which he threw a stone or ring. The task of the "proband"--the ordeal taker--was, as Bishop Eberhard of Bamberg's 12th century breviary instructed, to "plunge his hand into the boiling water" and pluck it out. Afterwards his hand should "be immediately sealed up." If he's innocent, he'll "bring forth his hand safe and unharmed from this water. But if he be guilty and presume to plunge in his hand," it will show burn injuries on inspection three days later.

The hot iron ordeal was similar, except the proband carried a piece of burning iron nine paces instead. The formula for deciding guilt was the same: If it burns you, you did it.

The cold water ordeal dispensed with the hot stuff in favor of a tepid pool. The ninth century theologian Hincmar of Rheims described it this way: "He who is to be examined by this judgment is cast into the water bound, and is drawn forth again bound." If he's guilty and "seeks to hide the truth by a lie," he "cannot be submerged." In other words, guilty people float. Innocent people sink.

Medieval law reserved ordeals for certain kinds of cases, typically those involving accusations of serious crimes, such as homicide, robbery, or arson. Punishments for failing them ranged from fines to mutilation to death.

The law also reserved ordeals for cases that judges couldn't confidently decide without them. "The ordeal of hot iron is not to be permitted except where the naked truth cannot otherwise be explored," 12th century English law decreed. Or as 13th century German law put it, "It is not right to use the ordeal in any case, unless the truth may be known in no other way."

If a defendant confessed or reliable witnesses testified against him, judges would convict him straightaway, without an ordeal. If enough acceptable "oath helpers" swore his innocence, he would be acquitted. But when such "ordinary" evidence was silent, judges unwilling to convict or exonerate accused criminals indiscriminately needed another way to determine how to rule. That way was ordeals.

These were justified on the grounds that they were indicia Dei--judgments of God. Where man couldn't correctly assign criminal status, he recruited the Lord. "The judges may decide that which they clearly know," a Carolingian capitulary directed, "but that which they cannot know shall be reserved for Divine judgment."

According to medieval Christian belief, if priests performed the appropriate rituals, God would reveal individuals' guilt by letting the boiling water or burning iron harm them or by making the holy water reject their guilty bodies; He would reveal their innocence by miraculously saving their limbs from harm or accepting their guiltless bodies into his blessed pool.

This may seem, well, stupid. But similar to King Solomon's baby-dicing idea, lurking below was a good deal of wisdom.

THE SECRET SOLUTION

CONTRARY TO WHAT you might expect, ordeals exonerated the majority of people who underwent them. That's right: Boiling water rarely boiled those who put their hands in it, and burning iron rarely burned those who carried it.

"If we suppose that few or none escaped conviction who exposed themselves to these fiery trials," the historian Robert Henry warns, "we shall be very much mistaken. For the histories of those times contain innumerable examples of persons plunging their naked arms into boiling water, handling red-hot balls of iron, and walking upon burning ploughshares, without receiving the least injury."

The Regestrum Varadinense, an ordeal register from Varad, Hungary, records the outcomes of 208 hot iron ordeals administered by clerics in the basilica of Nagyvarad between 1208 and 1235. Probands passed in 130 cases, or 62.5 percent of the time. Unless nearly two-thirds of ordeal-officiating priests didn't understand how to heat iron, something funny must've been going on.

Another source for ordeal outcomes is the English plea rolls, which were kept by the royal courts between 1194 and 1219. These contain outcomes for just 19 probands, but they point to the same phenomenon. Sixteen defendants underwent cold water ordeals; 14 passed. All three defendants who underwent hot iron ordeals were unscathed, too. Here, ordeals exonerated their takers 89 percent of the time.